Post on 01-Jan-2016
description
MODELING OF ENERGETICAL PROPERTIESOF BIS-AZO COMPOUNDS.
ROLE OF TAUTOMERIZATIONAlytis Gruodis, Nurija Kelminskienė
Department of General Physics and Spectroscopy, Vilnius university
Material
8th decade of XX century– electrophotographic dyes1th decade of XXI century– molecular device (SC!)(in poled polymer matrix, 1MV/cm)
Bisazo π-conjugated derivative – Stable, no photochemistry
2,7-diamino-fluorenone bisazo-pigmentum
NA1 , containing [-O-Me], EE,EQ,QQ conformers (tautomers)GU3 , containing two [–Cl], EE,EQ,QQ conformers (tautomers).
NA1 (R=[-C6H4-OMe])GU3 (R=[-C6H4Cl2]), where fluorenone is connected in position 2 and 7 via [-N=N-] bridge to quinine.
Main task
Probable geometry of molecule in layered structures
Explanation of experimental absorption spectrum
Molecular energetics
Technique of modeling• Quantum chemical methods• Gaussian09 software• 6/31G(d) basisset
Optimization of molecular geometryDensity functional B3LYP method
Calculation of electronic excitationSemiempirical ZINDO method for singlets only
Evaluation of charge redistribution Semiempirical TD method for siglets only
Intramolecular proton transfer
• Enol-Quinine tautomerisation• Trans-cis transition
Proton donor Proton acceptor
Second task
How many different forms? EE, EQ, QQ ?
Two molecular motions• 1) proton jump in tautomerization process allows the
existence of both - hydrazone-quinine form (Q) and azo-enol form (E);
2) conformational rotation of quinine fragment allows the existence of partially ’broken’ pi-conjugated system:
Generally, three type of different tautomers (EE, EQ, QQ) for NA1 and GU3 derivatives must be analyzed
Problem: EE, EQ, QQ ?
1. Geometry optimization
• Gaussian09
• B3LYP/6-311G(d,p) opt
NA1
GU3
Optimization of geometry• Three tautomiric forms: EE,EQ,QQ. Nine forms excludedEQ ir QQ – could be non-planar tautomers.
Benzene derivatives ( [-O-Me] ir [–Cl]) are oriented by angle 60 deg
2. Electronic excitation
Semiempirical ZINDO methodSTO-3G basis
Acid solutionBasis solutionBasis solution
3. Charge redistribution
What about CT state in region of 2 eV?
Gaussian09, TD(singlets,nstate=6) HF/6-31G sp
Charge redistribution between quinine, fluorenone and quinine,
Derivatives R are not included ( partial skeleton redistribution)
ConclusionsEQ form
Coexixtence of both: EE and EQ forms depending of the pH of media
Conclusions
1. Coexistence of both: EE and EQ forms depending of the pH of media
2. Fragmental rotation in range 30 deg (15 deg from equilibrium) like swinging. Excluding of band et 2 eV from 40 deg.
3. Partially broken pi-conjugated system 4. CT transition for EQ form
Thank you for attention